Gain Notes for Revolution 1255

This is one of the later revolutions in the mission where the calibration
sources have become so weak that for the best energy determination and
IC Gain History table is needed.

NB: This revolution contains a short period (IJD=4772.04 to 4722.18) during which the number
of incoming events more than doubles. To save telemetry, the JEM=X instruments automatically
increase the amount of grey filtering, which cuts down not only the number of source 
photons, but also the number of calibration events, meaning that the calibration spectra 
become very weak indeed. This period has been declared a BAD_RESPONSE BTI because no
useable calibration data has been received for this period. Experienced users can
overrule the BAD_RESPONSE BTI in the OSA hidden parameters if they wish, but this is not
recommended for other users, since poor energy calibration will affect no just the
assigned energy values for each event, but will affect the flux seen during this period.
The great drop in gain caused by the significantly increased countrate will drive
many lower energy events down into the low level cutoff, so that they are removed onboard
and never get transmitted. For both these reasons its best to avoid events from the BTI.
 

To get optimal results with this revolution it is necessary to use the IC gain history
table that has been created offline at DNSC, instead of the gain history table
created automatically by OSA. If you have the newest package of IC files from ISDC
and these are correctly installed, OSA will find the IC gain history table automatically
and you don't need to do anything else. The updated ISDC Instrument Characteristics
can be downloaded from
http://www.isdc.unige.ch/integral/download/osa_sw



However, if you don't have the IC gain table
package from ISDC you can download the table from the gain history archive by
anonymous ftp through the link provided. Download the table to some suitable
subdirectory for your analysis, then set the hidden OSA parameter gainHist:
gainHist="<my subdirectory>/<IC filename>". These files are used instead of the
automatically generated gain history tables wherever there has been an unusual or
non-linear behaviour of the detector gain.

	
JEM-X1: 

The Xe line analysis performed using the IC table shows excellent gain
correction with all SCWs except some weak misfitted science windows having a Xe level 
within 2% of the ideal. As usual however, it is recommended that users
avoid the first few science windows for energy-sensitive applications.
During the BTI period the gain is so low it cannot be corrected for, so this
period should be avoided for flux and energy-sensitive applications


Calibration source number 4 (purple/orange) is no longer
used for calibration purposes since an anode strip directly under the source
has broken and no useable signal comes from this area of the detector any
longer.


CAO 12/02/2013



JEM-X2: 

The Xe line analysis performed using the IC table shows excellent gain
correction with all SCWs except the very first science windows, the last SCWs and
one other point,  having a Xe level well
within 2% of the ideal. Apart from the very first SCWs, the other points are all
well within 3% of ideal. As usual however, it is recommended that users
avoid the first few science windows for energy-sensitive applications.
During the BTI there is no calibration data at all for this unit.

CAO 11/02/2013